Strip thickness control apparatus



June 1965 c. L. BRYAN ETAL 3,188,842

STRIP THICKNESS CONTROL APPARATUS Filed March 30, 1962 2 Sheets-Sheet 1 FLUID HEAT SOURCE EXCHANGER PUMP , 70 r 1W we CONTROL CONTROL MOTOR VALVE VALVE 4 MOTOR ,66 6| ,sa 26 RESET 1 l ,28 REFERENCE CONTROL CIRCUIT VALVE Moron 45\ v .-43 T 56' ss se 40 1 se 1 MOTOR 8213? AMPLIFIER SQEQ MOTOR RADIATION GAUGE IS/ l8 F I G.

warm-:ssss: INVENTORS QBM UQ Bernard P. McDonnell and 6 Chester L. Bryon.

June 15, 1965 C. L BRYAN ETAL STRIP THICKNESS CONTROL APPARATUS Filed March 30, 1962 GAUGE RADIATION 2 Sheets-Sheet 2 T/ROLLING MILL RESET REFERENCE CIRCUIT HEAT EXCHANGER United States Patent 3,188,842 STRIP THICKNESS CONTROL APPARATUS Chester L. Bryan and Bernard P. McDonnell, Cheektowaga, N.Y., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa, a corporation of Pennsylvania Filed Mar. 30, 1962, Ser. No. 183,790 3 Claims. (Cl. 72-12) The present invention relates in general to strip thickness control apparatus for a strip rolling mill, and more particularly to automatic strip thickness control appartus responsive to a measured strip thickness error for making a desired correction to minimize that error. When the strip is not positioned between the roller members the present control apparatus is operative to effect a fast reset operation for those roller members.

It is already known in the prior art to utilize a hydraulic work piston or movement member for effecting any desired change in the spacing between the roller members of a strip rolling mill. This work piston operates through a rack member and suitable gear device to adjust vertically positioned screwdown members that move at least one roller member as desired to provide the proper spacing between the roller members in contact with the strip passing through the strip rolling mill.

It is an object of the present invention to provide improved strip thickness control apparatus which is better and faster operative to position at least one roller member to provide the desired spacing between the roller members operating with strip material passed through a rolling mill, and further to be faster operative to provide a desired reset operation of the roller members when a given strip of material leaves the rolling mill in preparation for the entry of a succeeding strip of material.

It is an additional object to provide improved strip thickness control apparatus for a strip rolling mill employing hydraulic strip thickness control apparatus, wherein a first roll member positioning control device is employed for better correcting strip thickness errors when a given strip is positioned between the roller members, and a faster and better acting second roller member positioning control device is employed for an improved reset operation to effect a desired reset in the position of the roller members to a desired and predetermined initial or starting position when a strip of material is not positioned between the roll members.

In accordance with the teachings of the present invention, hydraulic roller member positioning and control apparatus is provided such that a first position control valve is responsive to any errors in strip thickness for the correction of those errors by suitable positional changes of the roller members while the strip is passing through the strip rolling mill, and a bypass control valve is responsive to the strip leaving the rolling mill such that the first position control valve no longer provides correctional movement of the roller members after the strip of material leaves the rolling mill. In addition, when the strip of material leaves the rolling mill, a suitable strip sensing member such as a roller member force sensing device begins the operation of a roller member positional reset device, such as a second and faster acting position control valve, to move the roller members to an initial reset position and prepare the rolling mill to receive a succeeding strip of material. A hydraulic pressure equalizer valve is operative with each one of the first control valve and the second control valve to allow any desired movement of the roller members to take place by the other of those control valves.

These and other objects and advantages of the present invention will become apparent in view of the fol- 3,188,842 Patented June 15, 1Q65 lowing description taken in conjunction with the draw-' ings wherein:

FIGURE 1 is a diagrammatic showing of the control apparatus in accordance with the teachings of the present invention; and

FIG. 2 is a schematic showing of a hydraulic embodiment of the subject control apparatus.

In FIG. 1, there is shown a rolling mill 10 including a lower roller member 12 and an upper roller member 14 operative with a strip of material 16 which is moving in the direction indicated by the arrow through the rolling mill 1%, onto a delivery windup reel 18. At a predetermined location relative to the rolling mill 10, a strip thickness measuring device, such as the radiation gauge 20, may be provided. In this regard, it should be understood that a roll force sensing transducer may be operative as a substantially equivalent device for this purpose with the rolling mill It) for an immediate measurement of the actual thickness of the strip 16 passing through the rolling mill 10.

A main piston 22 is operative with a screwdown mechanism 24 for effecting desired changes in the spacing between the roller members 12 and 14 for the purpose of correcting any thickness error in the strip 16 as sensed by the radiation gauge 20. For this purpose, a control valve 26 is operative with the motor 28 which receives thickness error signals from the radiation gauge for controlling the movement of the control valve 26 and thereby changing the position of the main piston 22 for the purpose of adjusting the screwdown or spacing between the roller members 12 and 14 for the purpose of correcting strip thickness errors. A fluid source 30 is operative with a high pressure pump 32 for supplying hydraulic fluid through the control valve 26 to the main piston 22 in this regard.

A roll force sensing transducer device 34 is operative to sense the force between the roller members 12 and 14 for providing an output signal through an amplifier 36 to indicate the presence or the absence of the strip 16 between the roller members 12 and 14. Morespecifically, when the roll force sensing transducer device 34 indicates the presence of the strip 16 positioned between the roller members 12 and 14, the output control signal supplied through the amplifier 36 causes the energization of a motor 38 operative to close a by-pass control valve 40 which would otherwise interconnect the hydraulic conduits 42 and 44 leading to the main piston 22. Similarly, when a strip of material 16 is positioned between the roller members 12 and 14, the output signal from the roll force sensing transducer device 34, which passes through the amplifier 36, is operative to energize a motor 4 6 connected to a control valve 48 to supply hydraulic fluid from the pump 32 through the control valve 48 to the main piston 22 depending upon the operation of the control valve 26, as will be later explained in greater detail. When the roll force sensing transducer device 34 does not indicate the presence of the strip 16 between the roller members 12 and 14, the motor 46 so operates the control valve 48 that the hydraulic fluid from the pump 32 is supplied through conduit 50 and the heat exchanger 52 back to the fluid source 30'.

When the roll force sensing transducer device 34 senses a strip 16 positioned between the roller members 12 and 14, its output signal passes through the amplifier 36 and energizes a motor 56 operative with a by-pass control valve 5? for causing that control valve 58 to interconnect the fluid conduits 6t) and 62 such that the reset piston 64 does not present a load to the movement operation of the main piston 22.

Also, when the strip 16 is positioned between the roller members 12 and 14-, the output signal from the amplifier r I 3,188,842 f Y with a motor 68 for maintaining closed a control valve 70 operative otherwise for Controlling the reset piston 64.

When the roll -force sensing transducer device 34 senses the absence .of the strip 16 between theiroller members 12 and 14, it provides an output signal through the amplifier 36 to the reset reference circuit 66 such that a predetermined or reference reset .positionfor the screw-down control device 24 is effected by suitable operation of the control valve 70 by'the motor 68. In this re'spechthe control valve 70 is now opened suchthat hydraulic fluid from the pump 32 is supplied to thereset piston .64 for the purpose of providing this predetermined reference reset position to prepare the rolling mill for the receipt of a succeeding strip of material to be passed be tween the roller members Hand '14.

When a strip otmaterial is not present between the roller members 12 and 14, the output signal from the amplifier 36 causes the control valve 26'to bepositioned such that the hydraulicfluid from the pump .32 passes directly into the-conduit 50 and back to the fluid source 30 through the heat exchanger 52. Als-o, at'this same time,.the motor 38 is operative to so position the control valve 40 such that the fluid conduits 44 and 42 as well as the fluid conduits 43' and 45 are commonly connected.

tial or reset position desiredfor the entry of a succeeding strip-of material'between the roller members 12 and 14 as shown in FIG. 1. This reset position for example may correspond to the screwdown setting that existed for the head end of the preceding stripand before error corrective positi-onchanges were'made, An auztotransformer operated synchro motor is suitablefor this purpose. The

The signal from the-amplifier 36 at this same time causes the motor 56 to so position the control valve 58 such that the conduits 60, 61, 62 and. 63 are no longer interconnected and therefore the control'valve 70'i-s operative to control the position of the reset piston .64 operative with the screwdown mechanism 24. I

In FIG. 2 there is shown schematically a hydraulic embodiment of the control apparatus shown'in FIG. 1. In FIG. 2, the fluid source is illustrated as a fluid sump. The pump 32 is operative tosupply high pressure fluid through a check valve 27 and the conduit 3-1 and the conduit 33 leading to the control valve 48. A higher pressure operative check valve 25 is provided as an emergency device. With the control valve 48 in the position as shown in FIG. 2, the conduit 3-1 is 'elrectively blocked by the measuringdevice, such as the radiation gauge 20 shown in FIG. 1. Depending upon the position of the control connected to the conduits 35 and 41. v "the same output signal from the roll force transducer-34 66 to'cause' the motor 68 to 'move the control valve 70 to a center position such that the conduits 37 and 39 are not At the same time,

passes through the amplifier '36and causes the motor 56 to move the valve 58 such that the conduits 37 and 39 are interconnected. This same signal'from the amplifier 36 causes the motor 38 to move the control valve 40 such that the conduits 57 and 61 areno longer interconnected through the control valve 40; At the same'time, the same output signal fromithe amplifier. '36 causesthe motor 46 to move the control valve 48 such that the conduit 31 is a .now operative with-the control valve 26 and the conduit valve 26, high pressure hydraulic fluid is supplied through i i a conduit 57 to the left-hand side of the main control pisvton 22 for movingthe control rod 59; in a direction to the right as shown in FIG. 2 for providing one of an increase in spacing between the roller members 12 and '14 shown-in FIG. 1or a decrease in spacing; depending upon the operation of the particular screwdown mechanism 24 provided forthe rolling mill 10. With the control valve 26 moved in the opposite direction, the conduit 61 is operative to supply high pressure, fluid to the right-hand side of the main control piston 22 such that the control rod 59 is moved ina direction to the left as shown in FIG.

2for effecting the opposite changes in the spacing between the roller members 12 and 14 shown in F IG.-1 When a strip of material is positioned between those roller members, the roll' force transducer 34 willprovide throu-ghthe amplifier 36 a control signal to the motor 38 for closing the by-passcontrol valve 40 which is shown open in FIG. 2

The control valves shown in FIG. -2 are illustrated in" ing the screwdown mechanism 24 to a predetermined ini- -33 is blocked by the control valve 48. Atthis same time,

the'strip thickness error signals. from the radiation'gauge 20 are effective through the motor 28 to move the control valve 26 either in the direction to' the right as shown-in FIG." 2. for causing thecontrol piston 22 to move the control arm 59 in a direction-to the right or in a direction .measured errors in the actua-lrthiokness of the strip passing through the rolling mill 10.

It should be understood that the hydraulic strip thick'ness control apparatus as shown in :FIGS. 1 and 2 lizing 'in conjunction an electric motorto reposition the roller members '12 and 14 for desired changesin the programmed thickness of the strips to be rolled in the rolling mill-10.1 For example, itmaybe desirable to provide a firstvthicknes's program for five strips ofrnaterialpassing through the rolling mill .10, and then change to a second and differentthickness program for 'the next five strips of material to be passed through the rolling mil-1'10.

The latterchange in desired @strip thickness may be ef- "fected by an electric motor which repositions through the screwdown mechanism '24 one or botlrof the roller members 12 and 14 as required to change' the initial or reset spacing between the-rollermembers12 and 14. "For this operation, it maybe necessary that the hydraulic control apparatusas shown in FIGS. 1 and 2 be operative to hold the control rods 59'and 71 in a-predeter- :vmined position such, that the rack '73 .and' cooperating 1 gear segments 75 and 77 .do-not change in position. This holding operation may 'be' readily'accomplished'by so energizing thermotors 38,and 56. such that therespectiv'e controlvalves 40Eand58 are closed suchas the control valve 58, 'isnshown in :FIG; 2. 'At the same time',;'the

-motors 68 and 28'which (control, the respective-control valves and 26 are'ropefrated to: causethe latter control valves tomaintain a neutral or middle position. This holding operation isaccompli'sh'ed asshown by the valve illustrations of FIG. 2. vThe.by.-pass valve 40 is in the open port position -connectinglin'es;57: and 161, while the valve 48 :is .in the position shown connecting fluid' lines 'circuit 66 positions the valve 70 so that the cylinder 64 is moved either to the left or to the right in opposition to any movement of the gear segments 75 and 77 from the reset reference position. The valve 7t) uses the high pressure fluid of the accumulator 29 to maintain the reference position.

It should be noted that the control apparatus of FIG. 2 is operative such that when the control valve 48 is closed by the motor 46, as does happen when the strip is not positioned between the roller members 12 and 14,

the output fluid from the pump 32 is effectively unloaded through the control valve 48 and the conduit 50 leading back through the heat exchanger 52 to the fluid source 30. For the purpose of prolonging the life of the pump 32 and lowering the power requirements necessary to operate the pump 32, the control valve 48 in the position illustrated in FIG. 2 in effect isolates the control valve 26 from the fluid accumulator 29, while by-passin g the hydraulic fluid through the conduit 5% to the oil source 39 at no load. The arrangement is such that the gallon per minute servo reset valve 70 is connected to the accumulator 29 and is instrumental in holding the gear segments 75 and 77 in their predetermined position at this time. Since the reset valve 70 is only rated 25 GPM as compared to 200 GPM of control valve 26, its approximately 6% leakage represents only a very small flow of hydraulic fluid. Since this can be supplied by the charged accumulator 29, the hydraulic pump 32 can be unloading during this time. When the hydraulic pump 32 unloads it essentially operates against no pressure and in effect idles. The pump manufacturers rate the life of a pump in the number of hours it operates against rated presure. Thus, the overall life of the pump 32 is increased directly by the number of hours it is unloading. It is estimated that the life of the pump 32 will be increased 46%) percent by this feature in a practical application of the present control apparatus.

The by-pass valve at the control cylinder 22 is energized, to connect fluid lines 57 and 61 thereby permitting this cylinder 22 to be in the idle position. When the accumulator 29 charge drops to a preset low point, a provided pressure switch monitors the energization of motor 46 of the valve 48 which shifts from the unloading cycle to an accumulator build-up cycle by blocking line 33 from line 50. The accumulator charge causes the valve 48 to return the system to the unloading cycle by connecting line 33 to line 50. This circuit arrangement gives the advantage of a longer unloading cycle, while still holding the gear segments in position. Since leakage through the servo valves is approximately 6% of rated flow capacity, the use of the small capacity servo valve 7%) and cylinder 64 for the holding operation permits a pump unloading period 8 times longer than if the larger valve 26 and control cylinder 22 were used for this purpose.

The unloading cycle functions as long as there is no strip of material positioned between the roller members 12 and 14. When a strip enters the rolling mill 10, the valve 48 is energized and the control circuit takes over. The unloading feature also permits the pump to be started and stopped at no load.

Although the present invention has been described with a certain degree ofparticularity, it should be understood that the present disclosure has been made only by way of example and that numerous changes in the details of the construction and the combination and arrangement of parts may be resorted to without departing from the scope and the spirit of the present invention.

We claim as our invention: 1. In strip thickness control apparatus operative with a source of hydraulic fluid for controlling a rolling mill having two roller members between which a strip of ma terial is moved to determine the thickness of that strip, the combination of strip position sensing means for providing a first control signal when said strip is positioned between said roller members, strip thickness measuring means for providing a second control signal in accordance with any thickness error between the actual thickness of said strip and a reference thickness for said strip, hydraulic position control means operative with said source of fluid and responsive to said second control signal for positioning at least one of said roller members to reduce said thickness error, hydraulic reset control means operative with said source of fluid and having a smaller capacity than said position control means and being operative for providing a predetermined reset position for one of said roller members, first ope-ration control means operative with said position control means and being responsive to said first control signal for enabling said position control means to respond to said second control signal, and second operation control means operative with said reset control means and being responsive to said first control signal for enabling said reset control means to provide said predetermined reset position for one of said roller members when said strip is not positioned between said roller members, and fluid accumulator means operative to supply fluid to said reset means when providing said predetermined reset position.

2. In hydraulic strip thickness control apparatus operative with a fluid source and a rolling mill having two roller members between which a strip of material is passed to determine the thickness of that strip, the combination of roll force sensing means operative with said rolling mill for providing a first control signal when said strip is positioned between said roller member, strip thickness measuring means operative with said strip for providing a second control signal in accordance with any difference between the actual thickness of said strip and a reference thickness for said strip at a predetermined location relative to said rolling mill, roller member screWdown control means including a first hydraulic movement member responsive to said second control signal for positioning at least one of said roller members to reduce said difierence for any strip present between said roller members, reset control means including a second hydraulic movement member for providing a predetermined reset position for one of said roller members, first operation control means including a hydraulic valve member responsive to said first control signal for enabling said first hydraulic movement member to position at least one of said roller members in response to said second control signal, and second operation control means including a second hydraulic valve responsive to said first control signal for enabling said second hydraulic movement member to provide said predetermined reset position for one of said roller members when the strip is not positioned between said roller members, and a fluid control valve operative with one of said first and second operation control means to bypass the fluid from said source away from said one control means in response to said first control signal.

3. In hydraulic strip thickness control apparatus operative with a fluid source and a rolling mill having two roller members between which a strip of material is passed to determine the thickness of that strip, the combination of strip position sensing means for providing a first control signal when said strip is in position to become operative with said roller members, strip thickness measuring means for providing a second control signal in accordance with any difference between a measured actual thickness of said strip and a reference thickness for said strip, spacing control means operative with said fluid source and being responsive to said second control signal for controlling the spacing between said roller members to reduce said difference, reset control means operative with said fluid source for providing a predetermined reset spacing between said roller members, first operation control means including a first fluid bypass valve responsive to said'first control signal for enabling said spacing control-means to respond t o said second control signal, and

second operation controlrneans including a second fluid Y bypass valve responsiveto said first control signal for enabling said reset control means to provide gsaidpredeterrnined reset spacing between said roller members when the strip is not positionedto be operative with said roller members, and a fluid control member operative with said spacing control means and responsive to said first controlsignal for isolating said fluid source relative to the spacing control means when the strip is not positian d lob pe vew said r le -m s a References :Cited by tlle Examiner UNITED STATES PATENTS v '80,56 .1

2,961,901 11/60 i Wheeler 4---, 80'-56.2 7 2,982,901 75/61 I Cannon 805 6.1 3,054,310? 9/ 621 Varner 80 56.3 

1. IN STRIP THICKNESS CONTROL APPARATUS OPERATIVE WITH A SOURCE OF HYDRAULIC FLUID FOR CONTROLLING A ROLLING MILL HAVING TWO ROLLER MEMBERS BETWEEN WHICH THE STRIP AND MATERIAL IS MOVED TO DETERMINE THE THICKNESS OF THAT STRIP, THE COMBINATION OF STRIP POSITION SENSING MEANS FOR PROVIDING A FIRST CONTROL SIGNAL WHEN SAID STRIP IS POSITIONED BETWEEN SAID ROLLER MEMBERS, STRIP THICKNESS MEASURING MEANS FOR PROVIDING A SECOND CONTROL SIGNAL IN ACCORDANCE WITH ANY THICKNESS ERROR BETWEEN THE ACTUAL THICKNESS OF SAID STRIP AND A REFERENCE THICKNESS FOR SAID STRIP, HYDRAULIC POSITION CONTROL MEANS OPERATIVE WITH SAID, SOURCE OF FLUID AND RESPONSIVE TO SAID SECOND CONTROL SIGNAL FOR POSITIONING AT LEAST ONE OF SAID ROLLER MEMBERS TO REDUCE SAID THICKNESS ERROR, HYDRAULIC RESET CONTROL MEANS OPERATIVE WITH SAID SOURCE OF FLUID AND HAVING A SMALLER CAPACITY THAN SAID POSITION CONTROL MEANS AND BEING OPERATIVE FOR PROVIDING A PREDETERMINED RESET POSITIION FOR ONE OF SAID ROLLER MEMBERS, FIRST OPERATIVE CONTROL MEANS OPERATIVE WITH SAID POSITION CONTROL MEANS AND BEING RESPONSIVE TO SAID FIRST CONTROL SIGNAL FOR ENABLING SAID POSITION CONTROL MEANS TO RESPOND TO SAID SECOND CONTROL SIGNAL, AND SECOND OPERATION CONTROL MEANS OPERATIVE WITH SAID RESET CONTROL MEANS AND BEING RESPONSIVE TO SAID FIRST CONTROL SIGNAL FOR ENABLING SAID RESET CONTROL MEANS TO PROVIDE SAID PREDETERMINED RESET POSITION FOR ONE OF SAID ROLLER MEMBERS WHEN SAID STRIP IS NOT POSITIONED BETWEEN SAID ROLLER MEMBERS, AND FLUID ACCUMULATOR MEANS OPERATIVE TO SUPPLY FLUID TO SAID RESET MEANS WHEN PROVIDING SAID PREDETERMINED RESET POSITION. 